U.S. Secretary of State John Kerry, left, talks with British Foreign Secretary Philip Hammond, right, as they meet with foreign ministers from China, Germany and France at an hotel in Vienna, Austria on Monday. (Carlos Barria/Pool Photo via AP)

VIENNA — As negotiators braced for yet another possible extension of nuclear talks, Iran demanded on Monday that any deal should include the end to a U.N. arms embargo as well — a condition backed by Russia but opposed by the United States as it seeks to limit Tehran’s Mideast influence.

Late last month, Iran and six world powers gave themselves an extra week past June 30 after it became clear that that original deadline could not be met. The sides now are trying to work out a deal that would limit Iran’s nuclear program in exchange for the easing of tens of billions of dollars in economic penalties on the Islamic Republic.

But disagreements persisted as the sides moved close to the new Tuesday deadline, and White House spokesman Josh Earnest said another extension was “certainly possible.”

Negotiators had previously mentioned the mechanics of curbing Iran’s nuclear programs and the time and pacing of economic sanctions relief as the most contentious problems. But an Iranian official — briefing reporters on condition of anonymity — said Monday that ending the arms embargo was an important part of the deal.

The Iranian decision to publicly bring that issue into the mix suggested that disputes ran deeper than just over the most widely aired issues.

A preliminary nuclear deal reached in April did not specifically name the arms embargo on Iran as part of the long-term accord. But a U.S. fact-sheet issued at the time said that the deal now being worked on would result in “the comprehensive lifting of all U.N. Security Council sanctions” on the Islamic Republic, which could be interpreted to include the arms embargo.

Still, the U.S. also said at the time that “important restrictions on conventional arms and ballistic missiles” would be incorporated in any new U.N. guidelines for Iran.

Both Russia and China have expressed support for at least a partial lifting of the arms embargo. Moscow, in particular, is interested in military cooperation and in Russian arms sales to Tehran, including the long-delayed transfer of S-300 advanced air defense systems — something long opposed by Washington.

The U.S. doesn’t want the arms ban ended because it fears Tehran could expand its military assistance for Syrian President Bashar Assad, for Houthi rebels in Yemen fighting a U.S. backed Arab coalition and for Lebanon-based Hezbollah, which opposes Israel. Lifting the embargo also would increase already strong opposition to the deal in Congress and in Israel.

With the arms embargo prohibiting both exports of weapons to Iran and exports by Iran — and Russia wanting to sell arms to Tehran — one possible solution would be lifting the ban only on importing weapons to the Islamic Republic and not on exports.

Iran also wants to have a hand in shaping any Security Council resolution that would endorse a comprehensive nuclear deal, if one is reached, the Iranian official said.

He offered no details but told reporters that Iran and Security Council members at the nuclear talks are drafting language for a proposed U.N. resolution and that Tehran is seeking a shift from the critical tone of previous resolutions on its nuclear program. All five Security Council members — the U.S., Russia, China, Britain and France — are at the table with Iran, along with Germany.

A U.S. official confirmed that a resolution text was being discussed at the talks. Both the Iranian and the U.S. officials demanded anonymity because they weren’t authorized to discuss the issue publicly.

The Iranian official spoke of good progress on some previously divisive topics. At the same time, he said some disputes may have to be resolved by the foreign ministers of the nations at the talks. All seven were either in Vienna or arriving by day’s end.

Over the weekend, diplomats reported tentative agreement on the speed and scope of sanctions relief for Iran in the potential accord, even as issues such as inspection guidelines and limits on Iran’s nuclear research and development remained contentious.

Iran says its nuclear ambitions are peaceful, but the U.S. and its allies fear the program could be turned toward making weapons.

With the deadline nearing, negotiators prepared Monday for a late-night session that diplomats said could extend into early Tuesday.

It’s in the Obama administration’s interest to have a deal by Thursday — if one is to be had. After Thursday, Congress’ time to review the deal grows from 30 to 60 days. President Barack Obama would have to await that review before being able to ease sanctions agreed to in a deal. Also in that period, lawmakers could try to build a veto-proof majority behind new legislation that could impose new sanctions on Iran or prevent Obama from suspending existing ones.